(1) Field of the Invention
The present invention relates to a vacuum switch and a vacuum switchgear, and especially to a vacuum switch with an electrically conductive vacuum container which is grounded or earthed and a vacuum switchgear using the same.
(2) Description of the Prior Art
Electric power demand in a central area of a large city increases day by day. On the other hand, there are problems such as difficulty in providing locations for distribution substations, difficulty in laying pipes for distribution lines underground and so on. Further, it is required that a substation is operated at the high availability factor.
To solve those problems, a distribution voltage has been raised, and increasing power demand is distributed to power lines with the larger capacity. Thereby, effective power supply installations can be realized. To this end, it is required to make devices for distribution and substation more compact.
As an example of compact substation devices, a SF.sub.6 gas insulation switchgear as disclosed in JP-A-3-273804 is proposed. According thereto, a circuit breaker, two sets of disconnectors and an earthing or grounding switch are manufactured independently, and therefore, they are accommodated in a unit room and a bus bar room filled with insulation gas such as SF.sub.6 gas. In a case where a vacuum circuit breaker is used as a circuit breaker, a movable electrode is moved by an operating mechanism up and down with respect to a stationary electrode, whereby a circuit is opened and closed. Further, in a vacuum circuit breaker as described in JP-A-55-143727, a rotatable electrode turns clockwise or counterclockwise, whereby a circuit is opened and closed.
A substation receives electric power from a power plant through a disconnector and a gas circuit breaker, changes the voltage thereof by a transformer to a voltage suitable for a load, and supplies the electric power to the load such as an electric motor. When devices in such a substation are inspected and/or maintained, power is cut by a gas circuit breaker and then a circuit is opened by a disconnector. After that, an earthing switch is operated to discharge any electric charge having remained in a bus bar to flow induction current to the earth, and the reapplication of voltage by the source is prevented to thereby secure the safety of a worker.
Further, if a bus bar with a charge is earthed or grounded before discharging, an accident may easily occur. Therefore, an interlock between an earthing switch and a disconnector is necessary to be provided.
The SF.sub.6 gas insulated switchgear disclosed in JP-A-3-273804 accommodates its gas circuit breaker, two disconnectors and the earthing switch in its unit room and bus bar room filled with SF.sub.6 gas as installed in its distribution cubicle. In the case where a vacuum circuit breaker is used as its circuit breaker, the movable electrode is moved vertically from its stationary electrode by means of an actuator of the vacuum circuit breaker thereby opening and closing the circuit. In the vacuum circuit breaker disclosed in JP-A-55-143727, a movable lead wire corresponding to a movable blade and a movable electrode are caused to swivel around a pivotal point of its main axis so as to contact with or separate from its stationary electrode, thereby closing or opening the circuit.
Furthermore, a conventional vacuum container has been made of insulator material, and therefore the container could not be earthed.